Heretofore, a wide variety of conductive materials have been used as coatings or fillers for various packaging materials to protect electronic components packaged therein from electrostatic discharges. For example, carbonaceous material such as particulate carbon black and graphite have been used as fillers in polymeric bags and films for packaging electronic components, and the same carbonaceous materials have been used to form coatings on paperboard boxes for the same purpose. Examples of such coated paperboard boxes are described in Ohlbach U.S. Pat. Nos. 4,160,503; 4,211,324 and 4,293,070. It is generally preferred to coat both the interior and the exterior surfaces of such boxes with the conductive material. It has also been proposed to use metal powders in a similar manner.
One of the problems encountered with carbonaceous coatings and metal powders is that the particulate carbonaceous or metallic material tends to slough off the packaging material, which can cause serious problems if the loose conductive particles happen to be deposited on sensitive electronic components. In an attempt to avoid such sloughing, coatings of such materials are sometimes sealed with a thin protective coating of another material.
Another problem with conductive coatings formed from carbonaceous materials is that it is difficult to control the surface resistivity of such coatings. Carbonaceous materials tend to produce coatings which have extremely low surface resistivities, and attempts to increase the surface resistivity by using smaller amounts of the conductive material result in discontinuities which render the coating non-conductive, or produce coatings having non-uniform properties over the surface area of a given container.